The present invention relates to a suspension system adapted to be arranged between members located on the body side and wheel side of an automobile, and more specifically, to an improvement in a car suspension system having an oil chamber and a gas chamber therein.
Prior art suspension systems, which are adapted to contain oil and gas, comprise a cylinder housing and a rod fitted therein. A gas chamber and an oil chamber are defined inside the cylinder housing. Compressed gas, such as nitrogen, is sealed in the gas chamber. The repulsive force of the gas acts as a gas spring mechanism. Damping-force generating means is provided inside the cylinder housing. The oil in the oil chamber is subjected to viscous resistance as it passes through the generating means, so that reciprocation of the rod is damped.
In this type of conventional suspension systems, a free piston is arranged between the oil and gas chambers, in order to prevent the gas from leaking from the gas chamber and being absorbed by the oil in the oil chamber. However, in systems which use a free piston, considerable frictional resistance is produced at the outer peripheral portion of the piston, as the piston moves. Moreover, the gas in the gas chamber is liable to leak out into the liquid chamber, through the peripheral portion of the piston. Therefore, it is difficult to completely prevent the gas from being absorbed by the oil.
As disclosed in U.S. Pat. No. 3,469,661 or 3,587,789, a suspension system has been proposed which uses a flexible cylindrical partition member. However, this partition member cannot satisfactorily prevent the gas from leaking from the gas chamber into the oil chamber. Therefore, prolonged use of the system may possibly cause a partial gas leak to occur, which would result in a reduction in the capacity of the gas chamber. If the gas chamber capacity lessens in this manner, the spring constant of the system will increase. Thus, if the system is used in an automobile, the vehicle becomes less comfortable to ride in, and its ride height will become lowered. To avoid this drawback, the gas chamber inside the cylinder housing must then be replenished with additional gas. Performing this replenishment, however, is difficult and time consuming.